A theory of heterosis.

This article focuses on the genetic basis of heterosis—the superior performance of hybrids compared to their parents—using a general multiple quantitative trait loci (QTL) genetic model called the G2A model. Applied to large maize and rice datasets, the study finds that heterosis in maize ear weight and rice yield is primarily driven by dominance effects of QTL, particularly overdominance, while the contribution of additive-by-additive epistasis is relatively minor. The model integrates additive, dominant, and epistatic effects jointly, enabling a comprehensive genetic interpretation of heterosis and offering insights for breeding design and selection strategies. The findings underscore the importance of dominance interactions in hybrid breeding and demonstrate the utility of the G2A model for quantitative genetic analysis in complex populations.